The fabrication of semiconductor devices often involves providing materials over a substrate and shaping those materials through processes such as photolithography and etching. For example, a dielectric material may be formed over a substrate using methods known in the art. The dielectric material may be patterned to form at least one opening through the dielectric material, exposing the substrate. This opening may be formed using a photolithography or etching process as known in the art. A conductive material may be formed in the opening to form a contact plug. The patterned dielectric material acts to electrically isolate adjacent contact plugs. However, because the substrate at the bottom of the at least one opening is exposed to air before forming the conductive material, a native oxide may foam on the substrate. Because this native oxide is an electrical insulator, if the native oxide remains on the substrate, the native oxide will hinder electrical communication between the substrate and the subsequently formed contact plug.
As a result, in-process devices at this stage of fabrication are often subjected to a cleaning process to remove the native oxide at the bottom of the at least one opening prior to forming a polysilicon material therein. The cleaning process may include a cleaning solution, such as at least one of QEII, MSe2, and ultradilute hydrofluoric acid (HF) (1000 parts water to 1 part HF). Either through immersion, spraying, vapor treatment, or other methods, the native oxide of the in-process device is exposed to and removed by the cleaning solution.
Unfortunately, while HF removes the native oxide from the bottom of the opening, the HF also may laterally etch the dielectric material that defines the opening. The result is that the diameter of the opening is increased. Widening the opening may be detrimental to semiconductor device fabrication because a wider opening means that there is less dielectric material separating adjacent conductive elements and an increased likelihood of a short between the adjacent conductive elements.
Accordingly, there is a need in the art for cleaning solutions and methods to effectively remove the native oxide without also removing a portion of the dielectric material.